The branch of biology dealing with fungi or diseases caused by fungus is known as mycology. In fact, mycology is among the earliest branch of knowledge pertaining to microbiology.
At the same time, it may be mentioned that fungi usually comprise the most common microorganism that is studied in microbiology.
Everyone is familiar with fungi for they have seen it grow in hair-like structures on decaying fruits and stale bread. And since the ancient periods, fungi have been used by man to produce fermented bread as well as alcoholic infusions.
That fungus is responsible for the decay of fruits as well as animal substance, has been identified by people since time immemorial.
In fact, fungi have been so closely related to the moldering organic substances that they have almost turned out to be identical with moldiness, disintegration as well as decomposition.
Fungi are present in an assortment of remarkable sizes - ranging from comparatively big and compressed organizations like puff-balls, mushrooms, toadstools and bracket fungi that found to be assailing decomposing trees by means of their various systems of strands in the soil, often related to the roots of plants, as far as the miniscule single-celled yeasts.
Nevertheless, all fungi are basically eukaryotic (single-celled organism whose cells contain a distinct membrane-bound nucleus) beings. As mentioned, the fungi cells have a nucleus and nucleoli bound by a membrane.
While their cellular respiration takes place in the mitochondria in the cytoplasm, the fungal cells also posses a complicated array of internal membrane structure.
Although the fungi demonstrate an amazing assortment of size and shape, they may be generally categorized in two groups - the yeasts and the moulds.
In fact, the moulds are also known as filamentous or mycelia fungi and they are made up of an arrangement of strands or filaments that are known as hyphae (singularly known as the hypha).
The hyphae are actually intertwined into a formation known as a mycelium (plural called mycelia). Actually, 'huphe' is a Greek term denoting a web, while the term mycelium has been drawn from the word 'mukes' denoting mushroom.
Moulds are capable of replicating themselves both by asexual as well as sexual procedures, while the fruiting and mycelium of any mould are together known as the fungal thallus, which translated into Greek means 'green shoot'.
The germ cells or spores of the fungi are very significant in recognizing the fungi.
Often the mycelia tissue is also known as an anastomosis (inosculation), as it encompasses a mesh of cross-connecting hyphae. In fact, the tips of the hyphae grow to develop into the mycelial formations.
In addition, these hyphae comprise filaments branching out now and then. The cytoplasm present in the infantile hyphae fills up the hollow space in the filaments.
However, further back from the developing tips of the hyphae, the cytoplasm has more and more vacuoles. In other words, they turn out to be more vacuolated at the tips.
In fact, the oldest hyphae are vacant formations that may even be detached from the remaining part of the mycelium.
When closely scrutinized, it is seen that in most of the moulds, the hyphae are separated into segments by the normal presence of cross-walls or septa (singularly known as septum).
These formations provide firmness to the strands or filaments as well as help to organize the passage of nutrients all the way through the complex arrangement of the mycelia.
Incidentally, the intricacy of the septa also differs - while a plain septa possesses a solitary central pore, a number of septa found in advanced fungi possess a dolipore (single double-layered membrane) arrangement wherein a slender central pore is bordered by pierced membranes called parenthesomes that resemble a cap and is composed of shapeless substances.
The separate sections present in the septate hypha may enclose a solitary nucleus and they are considered to be uninucleate or they may even possess multiple nuclei and are, hence, also known as multi-nucleate.
Phycomycetes, which are considered to be primitive fungi, do not possess any septa to segregate the hyphae into different segments.
On the other hand, the aseptate hypha is expressed as coenocytic - a term derived from the Greek word 'kinos' or 'kutos' commonly denoting a vessel.
Infrequently, the septa grows into Phycomycetes, however, their role is limited to detach the reproductive parts from the vegetative body of the fungus or to isolate the older segments of the thallus.
Very much different from the septa of other fungi, the formations detailed by the Phycomycetes are firm salvers and they never possess any central pore.
In some advanced variety of fungi, the neighboring hyphae are able to blend passively to produce a three-dimensional complex formation.
In fact, such three-dimensional formations give rise to reproductive fruiting bodies of the fungi. In addition, the hyphae also have the ability to develop other specific structures that display a great extent of internal organization due to synchronized development.
The rhizomorphs (a dense mass of hyphae forming a root-like structure characteristic of many fungi) are basically filaments resembling ropes and possess an extremely distinguished formation.
These arrangements seem to grow in response to pressure and in nature they grow in comparatively arid surroundings like the conditions present in sandy soils.
Fungi also possess a substance called sclerotia (singularly known as sclerotium) that are basically solidified formations that enable the moulds to remain alive even in an inactive or dormant condition.
By nature, sclerotia are colored and are large enough to be seen by the naked eye. Usually, they have a spherical shape, but may also appear in various asymmetrical forms.
The cells of the exterior walls of a sclerotium have broad walls providing the structure a substantial and defensive covering.
This thick, protective coat surrounds a central cortex of hyphae that enclose the food preserves needed during the period when it lies dormant. Usually, the food reserves or nutrients are preserved as glycogen or oil globules. Nevertheless, the most common formations produced by fungi are toadstools and mushrooms.
These fungi formations are extremely complicated structures that participate in reproduction of the microorganism and display an amazing degree of internal segregation as well as organization.
Usually, a stalk called stipe holds up the cap known as pileus and the gills of the fungi grow beneath this cap.
It needs to be mentioned here that these gills are responsible for releasing the spores or germs that cause fungal diseases.
In fact, the growth of these gills is an extremely harmonized procedure that reacts to ecological stimulus. It is essential for the gills to grow vertically for them to be able to release the spores effectively.
Such vertical growth of the gills is possible owing to geotropism (development of an organism in response to gravity).
Close observation of the development process of the gills have shown that if the developing formation is slanted, then the gills would develop vertically but in a lying position.
Usually, the fungal thallus in yeasts comprises of a solitary cell. In fact, yeasts are primarily single-celled fungi that vary in shape from round to oval or elongated. Even the size of the yeast may differ from two to approximately 10 micrometers.
It may be noted that only a restricted number of yeasts possess intricate additional cellular casings.
An instance of this type of yeast is the Cryptococcus neoformans - a pathogen that results in a chronic type of meningitis (inflammation of the meninges of the brain and the spinal cord) mostly found in patients affected by acquired immune deficiency syndrome (AIDS).
In such cases, the encasing or capsule mucopolysaccharide assists the yeast to avoid the body's defense mechanisms, and thereby, enables it to cause and spread the diseases.
In general, the reproduction of the yeasts involves an asexual budding process. In the first stage, the parental yeast cell enlarges to form a swelling or protuberance that expands into a fungal spore (blastospore) that ultimately detaches from its parent cell.
The term 'blastospore' has been derived from the Greek words 'blastos' and 'sprout' denoting a spore developed from a sprout.
However, in the fission (cell division to reproduce) yeasts like Schizosaccharomyces pombe, the parental yeast cell divides into two offspring in such as way that is slightly similar to the transverse or intersecting binary fission as in the case of reproduction of bacteria.
In fact, the yeasts hardly ever have a genuine multi-cellular arrangement. Some yeasts have an appearance of a series or chains of drawn out cells that are known as pseudomycelia (singularly know as pseudomycelium) or pseudohyphae (singularly called pseudohypha).
In fact, pseudomycelia are basically extended yeast cells that emerge from the buds sticking on together in branching successions.
Each separate cell present in a pseudomycelium is free from each other and, dissimilar to the units present in the septate hyphae of moulds, these cells are not connected with one another by means of pores.
Yeast cells possessing a normal unicellular structure may bunch at the terminations or alternately the length of the side of a pseudomycelium.
Such developments are known as secondary blastospores. At the same time, there are a number of yeasts that are able to fabricate septate - genuine mycelia under specific situations of growth.
While it is advantageous to segregate fungi into two categories - moulds and yeasts, there are several types of fungi that can adapt their arrangements in reaction to the modifications in their respective surroundings.
They have the capability to develop as mycelia or in a yeast form to a large extent based on the prevailing development conditions.
Such fungi that are able to adapt themselves in accordance with the environmental changes are known as dimorphic fungi.
It may be noted here that the mycelia created by dimorphic fungi are genuine mycelia and very dissimilar to the pseudomycelia formed by some other varieties of yeasts.
In fact, several of the dimorphic fungi are responsible for causing disease in the humans.
For instance, the dimorphic fungi called Candida albicans is responsible for causing the disease thrush (an ailment, especially occurring in children and characterized by whitish spots and ulcers on the membranes of the mouth, etc).
The Candida albicans fungus contaminates the mucous membranes, usually those present in the mouth and the genital tracts.
The most common and noticeable symptoms of thrush in the mouth include white plaques in the mouth, while the signs of vaginal thrush include prickly white vaginal ejections.
Fungi are often depicted similar to plants primarily because they are generally immobile and also because, like the plants, their cells are also enclosed by properly delineated and multi-layered cell walls.
Notwithstanding these two similarities, the arrangement of the cell walls of the plants and fungi are significantly different.
While the plant cell walls are made up of celluloses and hemi-celluloses, the cell walls of fungi are primarily made up of different polysaccharides, such as chitin - a polymer of N-acetylglucosamine.
In addition to being one of the main elements of the cell walls of the fungi, chitin is also a morphological polymer that is present in the exoskeleton (a hard outer structure or covering like a shell) of the arthropod invertebrates.
Polysaccharides form a major element of the cell walls of the fungi - both moulds and yeasts. In fact, as much as 80 per cent of the materials comprising the cell walls are crystalline micro fibrils in a shapeless matrix substance.
The remaining 20 per cent of the fungi cell wall components comprise of approximately equal extent of proteins and lipids. The nature of the polysaccharides composing the cell wall of the fungi largely depends on the type of the fungi.
Chitin is the major fibrillar element in moulds, while polymers of glucose called glucans comprise the amorphous of shapeless matrix substance in this case.
On the other hand, the yeast cell walls in the main comprise mannans - polymers of mannose. In addition, glucans are also present in the yeast cell walls.
In Saccharomyces cerevisiae, commonly known as the bakers' yeast, chitin is present below 1 per cent in the cell walls.
On the other hand, this polymer is mainly related to bud scars wherein it develops a mass of materials. Cellulose comprises the main structural element in the cell wall materials of Oomycetes, a special group of fungi contained by the Phycomycetes.
Generally, the cell wall of the fungi comprises five strata. This is best demonstrated by the structural design of the cell wall of the full-grown hyphae of the mould called Neurospora crassa. The foundation or base of the fungi cell wall is composed of plasmalemma.
On top of the plasmalemma, there is a layer of chitin micro fibrils that is present in an amorphous or shapeless milieu of proteins, glucans and mannans.
This layer is approximately 20 nanometers thick or wide. Outside the chitin micro fibrils, there is a separate layer of protein that has a width of around 10 nanometers.
The protein layer sustains a network of glycoprotein set in protein. The layer of glycoprotein in the fungi cell is approximately 50 nanometers thick.
However, the thickest layer of the fungi cell wall is the outer most stratums, which is composed of amorphous glucans and is around 90 nanometers thick, particularly in the fungus Neurospora crassa.
As discussed earlier, the reproduction or replication process in fungi may be both - asexual as well as sexual.
However, in either instance, the spores are the formations that are basically responsible for scattering the new offspring to develop colonies in fresh areas.
Some spores in the fungi are intended to endure or survive even in conditions not suitable for the microorganism's growth or even offer them a suitable environment for some time of dormancy.
In addition, the mycelia present in the moulds may also break up into pieces and each of these fragments may afterward grow into separate thallus by means of the vegetative reproduction method.
It may be mentioned here that the expression vegetative reproduction denotes a procedure where, apart from the spores, particular replication formations are not developed.
When a fungus reproduces by means of asexual or vegetative procedures it is known as anamorph, while fungus reproducing sexually is called teleomorph.
Owing to their resemblance, quite often people mistake fungi to be a type of plants. Nevertheless, plants are able to produce intricate organic amalgams from simple inorganic substances like water and carbon dioxide by means of a process known as photosynthesis.
On the other hand, fungi require complete organic compounds for energy generation as well as their development. Hence, fungi are expressed as heterotrophic organisms derived from two Greek terms 'heteros' and 'trophikos' denoting nourishment.
Therefore, it is evident that heterotrophs are nurtured from some other place, instead of themselves being able to nourish themselves in the manner of the autotrophic plants.
It may be mentioned here that majority of the fungi are usually in dark and moist environments, but are commonly present where organic substances are generally found.
As fungi may reproduce asexually as well as sexually, they may also be saprophytes (organisms surviving on dead organic matter) or parasites (organisms surviving on an organism of another species, known as the host, from the body of which it obtains nutriment).
The term saprophyte has been derived from the Greek terms 'sapros' and 'phuton' that denote dead plants. Similarly, word parasite has also been derived from the Greek expressions 'para' denoting other or beyond and 'sitos' meaning food.
Hence, parasites obtain their sustenance from other living organisms - plants or animals, and usually cause or pass on diseases on to their hosts. In fact, most of the fungi are present as saprophytes in the soil.
They survive on decomposing plant materials wherein they have a crucial role in the reprocessing organic substances.
Usually, fungi obtain their nourishment by exuding hydrolytic enzymes in their surroundings and these enzymes assimilate different polymers to manufacture soluble substances that the fungus is able to take up.
Fungi are also able to grow on a mineral salts agent enclosing a source of nitrogen salts in synthetic or stimulated culture. However, in this instance it is necessary that the mineral salt medium possesses glucose as a source of carbon.
The presence of glucose enables the fungi to produce all the intricate organic molecules they require for growth by the metabolism of glucose.
On the other hand, other types of fungi need an external supply of vitamins or other developmental aspects which they themselves cannot produce with the purpose of growing in synthetic or stimulated conditions/ culture.
Provided the vegetative cells in an artificial culture are required to initiate production of spores, the fungi essentially require additional growth aspects.
It may be noted here that the fungi have a particular need for trace elements, such as iron, calcium, copper, magnesium, manganese and zinc, to grow in artificial culture and otherwise.
However, thus far scientists have not identified any fungus that is able to fix nitrogen from the atmosphere.
The most important polymer used by fungi for storage purpose is glycogen. However, they also use oil globules for storage of nutrients.
Akin to other eukaryotes, fungi also require air or oxygen for free breathing and they acquire energy from the aerobic respiration of glucose.
Nevertheless, a marginal species of yeasts are equipped to survive under different sets of conditions and do not require air for respiration.
In other words, they are able to survive in anaerobic conditions and acquire their energy from fermentation. However, this procedure is not as effectual as aerobic respiration.
In artificial culture, approximately 1 per cent of the transformed baker's yeast or Saccharomyces cerevisiae is found having no mitochondria. As a result, these fungi cells are unable to carry out respiration as they are incapable of pulling mitochondria together.
Therefore, when they develop on any glucose-based firm medium, they are able to get the requisite energy only by means of fermentation.
In fact, compared to the wild kind of cells that enclose mitochondria, such transformed or altered cells usually develop quite small colonies. Hence, these types of cells are also known as petite mutants.
While many may think that classification and identification of different organisms is the same thing, actually they are not only singular, but correlated procedures. Classification denotes separating organism according to their characteristics of a hierarchy.
This process depends on the extent to which the organisms are related to each other. On the other hand, the procedure of identification involves grouping different isolated organisms within a specific categorization format.
It is not an easy task to classify microorganisms and the parasite Pneumocystis carinii is a case in point.
For many years, this parasite was considered to be a protozoan. This parasite is responsible for developing pneumonia in humans and its victims are primarily people who are incapable of developing a normal immune response or immunocompromised.
In fact, pneumonia is the most widespread life-threatening disease in people enduring AIDS. Pneumocystis carinii is a single cell flagellate (producing filiform runners or branches resembling runners) being that does not possess any cell wall.
Nevertheless, latest molecular genetic researches have demonstrated that compared to other protozoa, Pneumocystis carinii is actually more intimately related to the fungi.
Scientists have come to this conclusion depending on the arrangement of the organism's ribosomal RNA molecules - an aspect that is usually made use of in molecular taxonomy.
It may be noted here that the classification of moulds or mycelial fungi is basically done in consistent with the organism's macro and micro morphology (form and structure). However, comparatively the yeasts have a simpler formation and hence, they show a restricted variety of morphologies.
As a result, it is quite difficult to categorize yeasts and therefore, they are classified partially depending on their responses in biological experiments. In fact, there is no unanimously agreed method to classify fungi.
According to a number of methods to categorize fungi, the sharing out of fungus is known as phyla. In addition, some methods of classification have actually realigned the fungi categorized in the Phycomycetes.
Moreover, constituents of the fungi belonging to the Myxomycota and Mastigomycotina have been rearranged into the Protoctista kingdom that also comprises protozoa and nucleated algae. Many experts even do not recognize these varieties as genuine fungi.
On the other hand, fungi belonging to Zygomycotina have been maintained as a cluster in the fungal territory and are known as the Zygomycota.
The slime moulds, known as the Myxomycotina, are distinguished by an ameba-like vegetative phase.
Conversely, when the conditions are suitable, the amoeboid cells gather together and make a distinction to develop reproductive formations that appear similar to other fungi.
Therefore, developmental biologists examine members of the cluster of fungi comprising Physarum polycephalum and Dictostelium discoideum in an exhaustive manner.
In fact, slime moulds are generally free-living beings present in places such as leaf waste and soils. Nonetheless, a number of slime mould species are also found as parasites.
Most often the parasites are found associated with higher plants, other fungi as well as algae, inclusive of the marine algae.
The parasite called Polymyxa graminis, which does not cause any symptom, is usually found connected to the roots of cereal crops and is also able to function as vector for viral diseases.
The Mastigomycotina is a type of fungi that forms or produces zoospores or asexual spores. This type of fungi is able to form branched cell chains that bind to the surface of their host by means of a structure resembling a root and is called rhizoid.
Many species of these fungi are basically soil saprophytes where they perform a vital function of decomposers. On the other hand, the Mastigomycotina is also found in fresh water environment, and may also be related to water that is contaminated with sewage.
While some of the species of these types of fungi are present in nature as parasites of fish and insects, while there are other species that are found as parasites surviving on plants and algae.
The downy mildews are obligate parasites that are not capable of developing in normal laboratory cultures.
This group of obligate parasites comprises the notable plant pathogens like Phytophthora infestans and they are responsible for causing potato blight (any of a range of highly destructive fungus diseases of the potato).
On the other hand, the Zygomycotina are very familiar soil saprophytes and a number of species of this type of fungi are found in the animal excreta. Fungi species belonging to the genus Entomophthora are parasites that survive on houseflies and aphids.
In addition, the Zygomycotina also comprise a very significant cluster of fungi that are able to develop symbiotic relations with higher plants, which are called mycorrhizas.
These formations entail a very close relation between a fungus and the root system of the plant it is associated with.
For instance, orchids possess mycorrhizal relationship with fungi in their root system.
In this kind of association, while the fungus obtains its organic nourishments from the plant it is associated with and, in return, is supplied with the mineral nourishments that the mycorrhiza obtains from the adjacent soil.
It may be mentioned here that it is almost impossible to develop any fungus that forms mycorrhizal relations with higher plants in a stimulated or artificial culture.
The genus Ascomycotina comprises yeasts similar to those belonging to the genus Saccharomyces.
The type of yeasts belonging to this genus includes Saccharomyces cerevisiae that forms the foundation of the baking as well as brewing industries. Hence, these yeasts are very important from the commercial point of view.
Normally, yeasts are mostly related to fruits, but they are also present in freshwater as well as marine surroundings. In fact, the mycelial Ascomycotina are very widespread soil saprophytes and may also be found in animal excreta.
On the other hand, fungi belonging to the genus Tuber are capable of forming mycorrhizal relations with the root systems of different trees.
The fruiting parts of this type of fungi are reaped as truffles (any of several subterranean, edible and ascomycetous fungi of this genus) that are extremely valued as gastronomic delicacies.
It is interesting to note that in France pigs are specially trained to locate truffles by the smell emitted by these edible fungal parts.
However, not all varieties of Ascomycotina are beneficial or safe for consumption. The ascomycete fungi are responsible for causing mildews of roses, while Ceratocystis ulmi causes the disease known as Dutch elm that destroys the elm trees in England.
Similarly, the dermatophyte fungi are responsible for causing diseases like ringworm and athlete's foot. All these types of fungi, including the dermatophyte, are grouped as members of the Ascomycotina family.
The genus Basidiomycotina comprises a number of fungi that survive developing mutually beneficial alliances with plants.
While a few of the species are responsible for causing diseases, the majority of them are saprophytes and are usually found growing in composts, soil, animal excreta and leaf waste.
Fungi belonging to the genus Agaricus are capable of forming fairy rings or rings originating from mycelial growth. Several of these fungi also form mycorrhizal associations with higher plants, especially trees.
In fact, the species of fungi called Merulius lacrymans is responsible for dry rot in timber. Basidiomycotina belonging to the group Teliomycetes comprise fungi that cause smuts or plant rusts.
However, they are often important from the economic point of view, as they normally have an effect on cereal crops. As the name implies, fungi belonging to the category of Gasteromycetes comprise a group of fungi that are edible.
Fungi Imperfecti or the Deuteromycotina inevitably comprise an assortment of saprophytic as well as parasitic fungi. Many fungi, such as those similar to the genera Aspergillus, Penicillium and Cladosporium, are notable fungi that work to spoil foods.
Aspergillus flavus as well as associated species of fungus are responsible for the production of alfatoxin and the presence of this poisonous substance in foods is very worrisome, as alfatoxin belongs to the group of most potent carcinogens discovered thus far.
On the other hand, the fungal species known as Aspergillus fumigatus is liable for causing the disease aspergillosis in humans.
Some types of this disease may result in grave and sometimes even fatal contagion in people who are immunocompromised or have a poor immune system. Especially, transplant patients are most vulnerable to this disease.
Nevertheless, the species Aspergillus niger is of immense economic value, as it is made use of in the industrial production of citric acid. Likewise, members of the genus Penicillium are vital in manufacturing antibiotics.
While Penicillium chrysogenum is utilized in the industrial production of anti-bacterial antibiotics belonging to the penicillin family, another species Penicillium griseofulvum is made use of to manufacture the anti-fungal agent medication called griseofulvin.
The process of identifying a mycelial fungus entails the study of its macro as well as micro morphology (cell structure and formation). These aspects differ on the basis of the medium on which the microorganism grows as well as the temperature applied to cultivate a mould.
Therefore, it is frequently essential to grow a fungus on an assortment of media with a view to obtain its entire classification. It is essential to carefully examine the dyed surface of the mould colonies.
While these aspects (the colored textures) may vary from one area of the mould colony to another, they may also be different on the exterior and the beneath of the colony.
At the same time, careful note should be taken of the special formations, such as the fruiting bodies, sclerotia and others.
Prior to unsettling the colonial development of moulds with a view to make microscopic research, the complete culture may be scrutinized by making use of a low-power aim in order to examine the fruiting bodies situated in the original, natural or existing place or position (in situ).
Subsequently, lactophenol or lactophenol cotton blue build ups ought to be made from the mould colony. A separate mount needs to be prepared from every area of the colony that displays a dissimilar macro-morphology or structure and form of the mould.
In order to observe all the structural aspects related to a specific fungus, it is essential to have a number of mounts from all diverse areas of the mould colony.
It is essential to have a precise examination to obtain a successful detection of fungus developing in a simulated or artificial culture.
It is frequently necessary to make use of specific culture procedures like slide or cellophane cultures in case a fungus possesses frail spore formations. Doing so will enable one to properly examine the micro morphology of the particular fungus without any trouble.
Sometimes it may be tricky to differentiate the fruiting structures of a fungus, such as perithecia, pycnidia, sclerotia and cleistothecia from one another.
While it is easy to differentiate or identify a number of sclerotia in some fungi owing to their asymmetrical form, while it is difficult to make a distinction in other fungi.
The most excellent method to make out these formations is to crush them to find out what emerges from them. However, at times it is not easy and almost impossible to crush sclerotia.
It may be mentioned here that when sclerotia is crushed, it give away a number of oil globules.
On the other hand, when pycnidia are crushed, it releases a large number of conidia. Similarly, cleistothecia and perithecia release asci and ascospores when squashed. In fact, both asci and ascospores appear to overflow from the fruiting structures of the fungi.
As discussed earlier, the yeasts have a comparatively uncomplicated formation, but it is indeed an irony that this makes it even more difficult to identify them in comparison to other types of fungi.
Classification of yeasts is basically done on the basis of some degree of dissimilarities in their cell structure or cytological differences as well as depending on their biochemical features.
The cytological aspects utilized while identifying the yeasts comprise issues such as the size of the cell, form of the cell as well as whether it possesses a capsule or not.
A number of yeasts have the ability to produce pseudohyphae, while a marginal number of them have the ability to produce genuine septate mycelium that are similar to those present in moulds.
At the same time, a number of yeasts are also competent for sexual reproduction to turn out ascospores (a spore formed within an ascus).
On the other hand, very few types of yeast reproduce sexually to generate basidiospores (a spore that is borne by a basidium).
Cryptococcus neoformans, the yeast that is enclosed in a capsule and is responsible for causing meningitis (inflammation of the meninges), especially among patients enduring AIDS, belongs to the Basdiomycotina family of yeasts.
Candida albicans is a significant commensal organism that co-exists with other organisms, but, as far as humans are concerned, it is a very opportunist pathogen.
It is able to identify this yeast from scientific specimens owing to its capability make a mycelial (the mass of hyphae that form the vegetative element of a fungus) microbe tube when it is nurtured for a duration of one to two hours in serum at 37°C.
In fact, the biochemical examinations entail monitoring the aptitude of the isolate to absorb a number of chemicals, especially sugar and nitrogen sources. In addition, the isolate's ability to ferment dissimilar sugars is also observed during the biochemical tests.
Presently, the classification process of yeasts has been regularized and one may avail a variety of strips from the market that can be immunized to examine absorption of carbon as well as nitrogen.
A classification summary of yeasts may be prepared on the basis of using the arrangement of substrate (surface on which the yeast grows or is attached).
In addition, the characteristics of the yeast may also be got hold of by referring a manual on the subject or making use of a database in a computer.
Several poisonous chemicals produced by fungi, including Aspergillus flavus and A. parasiticus, are associated with the occurrence of different incidents of animal poisoning.
Scientists first stumbled upon these toxins way back in 1960, when as many as 100,000 turkeys in England succumbed to food poisoning after consumption of peanut meals infected by moulds.
Incidentally, all these turkeys were imported from South America and Africa. The poisonous amalgams produced by fungi fragrant chemicals that are exclusively produced by them provided the heat and humidity are suitable.
For example, the most favorable temperature to produce the poisonous substance known as aflatoxin seems to be approximately in the range of 24°C to 28°C, while fungi that develops at temperatures lower than 15°C or at humidity at more than 75 per cent will not be able to manufacture such toxins.
In fact, when experiments were conducted in the laboratories, aflatoxins by fungi was very irregular, and researchers are of the opinion that apart from the temperature and humidity aspects, even other aspects like specific nutrients too establish the production of the toxin.
In fact, aflatoxin has been detected in a number of foods, usually in foods having their origin in agricultural produce, for instance grains, nuts, flour, meat and cheese available in normal atmospheric temperature.
These toxic materials appear to work by attaching to the DNA and encouraging transformations or mutations that subsequently turn out to be deadly or life threatening.
During the course of researches, scientists have discovered that the liver is particularly vulnerable to the poisonous substance called aflatoxin produced by fungi, such as Aspergillus flavus and A. parasiticus.
Indirect or incidental proof relates these poisonous substances to diseases caused to humans, but thus far scientists have not been able to establish anything concrete in this regard.
Irrespective of whether the fungi are an eukaryote or a prokaryote, the cytoplasm forms the medium of any of the organism's cell. In fact, the cytoplasm in an eukaryotic cell can be easily differentiated owing to the presence of diverse membranous formations known as organelles.
The best examples of such organelles are mitochondria and chloroplasts that are placed within the cell for carrying out different metabolic and other activities. On the other hand, prokaryotic fungi cells do not possess any organelle.
Instead they enclose several types of particle for providing nourishment to this type of fungi cell. It may be mentioned here that the different chemical activities within the cell (metabolism) as well as digestive activities usually take place in separate vacuoles within the fungi cell.
The cytoplasm of both eukaryotes and prokaryotes encloses ribosomes, even though they are of a different type. In fact, the cytoplasm enclosed by the cell membrane is the place for all types of cellular actions, barring the DNA replication and RNA code transcription. The prokaryotic cells that do not enclose any nucleus, even the DNA replication and the RNA transcription also occurs in the cytoplasm itself.
Fungi species belonging to the genera Epidermophyton, Trichophyton and Microsporum are virtually present everywhere in nature and are responsible for contaminating the skin, hair and nails of the living animals, including their human hosts, and result in severe inflammatory diseases called dermatophytosis.
In layman's terms, this condition is also known as ringworm or tinea owing to their medical manifestation. It is interesting to note that dermatophytosis is generally categorized on the basis of the parts of the body it infects and not according to the species infecting their hosts.
Therefore, the term tinea pedis denotes an infection of the foot, such as athlete's foot, while tinea capitis has an effect on the scalp and tinea unguium denotes the infection of the nail coatings.
It has been found that usually the species belonging to Microsporum have a penchant for infecting hair and nails, while those belonging to Epidermophyton generally contaminate the skin and sometimes also the nails. However, they never infect hair. On the other hand, species belonging to Trichophyton are capable of infecting all the three places - skin, hair and nails, with almost the same ability.
In fact, it has also been found that a lesion may contain more than one species of fungi. Each and every dermatophytes produce several proteolytic enzymes that help them to decompose keratin - the primary protein in the exterior tissues, and thereby, inhabit the host.
Usually, the compounds produced and secreted by the sweat glands slow down the action of these microorganisms, but they eventually overcome this opposition by infecting the hosts in abated conditions as well as in places where the presence of sweat glands is poor.
When such an infection takes place, the initial reactions are owing to inflammatory responses that result in the development of erythematous (redness of the skin caused by dilatation and congestion of the capillaries), flaking or vesicular lesions at the place of the contamination.
Eukaryotes are living beings that have cells possessing a nucleus - a particular compartment bound by a cell membrane accommodating the organism's DNA substances, i.e., genes, discretely from the remaining part of the cellular medium called the cytoplasm.
It is possible to differentiate the nucleus as well as the cytoplasm of eukaryotic cells under a simple light microscope using discriminating colorants. Apart from the nucleus, the eukaryotic cells also enclose particular structures or diminutive organs within the cell membrane that are called organelles that are responsible for carrying out different functions that are necessary for the cell to remain alive.
The primary functions of these organelles include respiration, metabolism and synthesis. The world of eukaryotic cells comprise a large assortment of organisms, including single celled microbes like yeasts and algae and multi-cellular macroscopic beings, such as plants, corals, fish, sponges, birds as well as humans.
Filovirus denotes a family of viruses that comprise agents of specific viral hemorrhagic fever (arbovirus infections, such as dengue, distinguished by fever, chills, malaise and subsequent hemorrhages of capillaries, occasionally resulting in kidney failure and even death).
In fact, filovirus are considered to be recently surfacing disease-bearing microorganisms that have acquired importance only during the past few years. The more familiar members in this virus family include the Marburg and the Ebola viruses.
From the structural point of view, these pathogens appear similar and seem to have long filament-like formations comprising a spiral nucleocapsid (the nucleic acid core and surrounding capsid of a virus) inside a firmly attached lipid covering with viral proteins on the exterior. The filovirus' genetic material or genome is horizontal with a solitary strand of RNA molecule of negative polarization with free ends.
Each filovirus is different from another of the species relating to their respective mechanism to stipulate production of antibodies in the host. When an individual is infected by filovirus it usually results in the development of hemorrhagic fevers with symptoms of severe fevers, debility of muscles, pains and headaches.
Within two to 22 days of being infected by filovirus, the patients experience systemic symptoms like vomiting, diarrhea, pharyngitis or sore throat and a rash that engulfs the entire body.
The hemorrhagic symptoms of the infection become apparent quite quickly, around the third day of the contamination by the virus and the patient experiences petechiae or pinpoint bleeding as well as bleeding all along the gastrointestinal tract.
It may be mentioned here that among all the viruses that cause hemorrhagic fevers, the highest rate of fatality is caused by infections by the Ebola and Marburg viruses. In addition, the symptoms of the hemorrhagic fevers caused by these two deadly viruses are also considered to be the most acute.
While the scientists are yet to develop specific medications or vaccines to combat and cure the life-threatening diseases caused by these viruses, diagnosis of the disease is possible by means of virus isolation or by serological examinations (blood tests undertaken to detect the presence of antibodies against any microorganism). Hence, in such cases the healing is primarily caring.
Scientists are yet to ascertain as to how the humans precisely acquired the Ebola infections. This is primarily owing to the fact that despite several efforts, they are yet to identify the natural host of this virus.
It may be noted here that the first instance of an outbreak of the Marburg virus was linked to the handling of contaminated tissues from a group of African green monkeys exported to Germany. Usually, infection by filovirus takes place by means of close contact, including sexual intercourse, between the infected individual and a healthy person.
Therefore, measure to contain the infection includes diminishing close contacts with people infected by the deadly viruses. Significant precautionary measures usually undertaken to prevent any accidental outbreak of the viruses include cautious handling of scientific and laboratory specimens, proper handling as well as discarding of laboratory equipment and substances, especially those in primate laboratories.
Flavivirus are a family of mainly RNA viruses transmitted by arthropods (tick-borne) that are related to human ailments, such as yellow fever, viral encephalitis and dengue.
These diseases are considered to be the most significant ailments plaguing the developing world. Initially, the flavivirus were categorized under the arbo-virus (any group of RNA-containing viruses that are transmitted by blood sucking arthropods) class as the Group B viruses, but later, they were detached and considered as an autonomous family on the basis of genomic characteristics, anti-genicity as well as their reproduction methods.
Presently, this family not only comprises members of the original arbo-virus species, but also specific diseases that are not transmitted by arthropod members, such as the hepatitis C virus and a number of specific veterinary pathogens known as pestiviruses.
Basically, viruses are spherical in appearance and enclosed elements possessing an inner hub composed of a solitary protein bounded by a firmly attached lipid covering obtained from the host.
Speaking in biological terms, the flavivirus genome or a full set of chromosomes having a single strand, positive-sense RNA molecule that is of approximately 11 kilo-bases and when exposed, it has the aptitude to infect other cells on its own. Reproduction of flavivirus takes place in the cytoplasm as it does not possess any nucleus.
The hypha is actually a strand or filament of a multi-cellular fungus. The usual vegetative hyphae are horizontal and may be septate with individual cells or a mass of uninterrupted multi-nucleate substance. Air-borne hyphae normally signify the reproductive parts of a fungus that are also known as spore-bearing fungus.
Segments surrounded by membranes, something that are solely found in eukaryotic cells, have a crucial role to play as they accommodate the entire genetic data that is necessary for a living being in order to survive. The major element of the nucleus is definitely the cellular DNA enclosed in one or more chromosomes based on the type of organism.
Moreover, the nucleus may even possess specific proteins that bind the DNA, such as histones and a variety of nucleic-acid-polymerizing enzymes. In fact, such compartments are actually places for the reproduction of DNA and also for the recording or transcription of the genes into RNA for the duration of the gene expression and synthesis of protein.
Actually, the nuclear membrane is a phosphor-lipid bilayer possessing two different countenances - nuclear and cytoplasmic - enclosing fixed proteins and pores that provide passages for communication between the nucleus and the remaining parts of the cell or cytoplasm. Using a selective strain under a normal light microscope, one may very easily observe the nuclei of a number of cells.
